1. Field of the Invention
The present invention relates to a charging member for charging the surface of an electrophotographic photosensitive member as a member to be charged up to a predetermined potential by applying voltage to the charging member, and a process cartridge and electrophotographic image forming apparatus (hereinafter referred to as an “electrophotographic apparatus”) using the charging member.
2. Description of the Related Art
An electrophotographic apparatus using electrophotography mainly includes an electrophotographic photosensitive member, a charging apparatus, an exposure apparatus, a developing apparatus, a transfer apparatus, a cleaning apparatus, and a fixing apparatus. For the charging apparatus, contact charging apparatuses are often used which apply voltage (voltage of only DC voltage or voltage of AC voltage superimposed onto DC voltage) to the charging member disposed in contact with or in the vicinity of the surface of the electrophotographic photosensitive member to charge the surface of the electrophotographic photosensitive member.
For more stable charging of the electrophotographic photosensitive member by contact charging, Japanese Patent Application Laid-Open No. 2003-316112 and Japanese Patent Application Laid-Open No. 2009-175427 disclose charging members for contact charging including a surface layer having a protrusion derived from a resin particle or the like in the surface of the surface layer. Use of such a charging member leads to more stable charging of the electrophotographic photosensitive member. As a result, unevenness in an electrophotographic image, that is, horizontal streaks, which may be produced due to ununiform charging of the electrophotographic photosensitive member, can be suppressed.
The reason of stable charging of the electrophotographic photosensitive member by using the charging member having the protrusions formed in the surface thereof leads is presumed that protrusions form slight gaps in a nip between the charging member and the electrophotographic photosensitive member, and discharge occurs in the gaps (Japanese Patent Application Laid-Open No. 2008-276026).